atmospheric chemistry: CH 4 to CO2 equiv

[RBryenton]

Hello. Need some help please, convert Tg CH₄ to Gt of CO₂.
UN says 9.8 Gt (CO₂-e) of methane emitted in 2023.
Canada source says 575 to 669 Tg of CH₄ emitted: average would be 622Tg. That is 622 Mt of CH₄.
Use 100yr (not correct) value of 28 for ch4 to co2-e = 17.4 Gt.
Somehow 9.8 Gt CO₂-e is supposedly equivalent to 622 Tg of CH₄.
What am I doing wrong please? Thank you. Roger

[ChenBeier]

Don't know US abbrevation.

What is Tg, Gt, Mt, the -e in CO₂-e

1 mole CH₄ molar mass 16 g/mol correspond to 1 mole CO₂ = 44 g/mol
If the abbrevations are mass units.

Gt = Gigatons = 10^12 Tons = 10^15 kg = 10^18 g

So 622 Gt CO₂ would be 622 * 10^18g / 44 g/mol = 14,13 * 10^19 mol
This value times 16 g/mol would 14,13 * 10^19 mol*16 g/mol =226,2 Gt CH₄.
17,4 Gt CO₂ is equal 6,32 Gt CH₄
9,8 Gt CO₂ is equal 3,56 Gt CH₄

Somehow 9.8 Gt CO₂-e is supposedly equivalent to 622 Tg of CH₄.

9,8 Gt = 622 Tg what does Tg mean

[RBryenton]

Thank you. Tg is tera grams. 1 Tg = 1 Mt.

[ChenBeier]

Ok
But that means 1 teragramm = 10^12 g
And 1 Mt = 1 Megatons = 10^9 kg = 10^12 g
So both units are equal.
The ratio of CO₂/CH₄ is 44/16 = 2,75
1 Mt CH₄ = 44/16 = 2,75 Mt CO₂
So 9,8 Gt = 622 Tg is wrong

[RBryenton]

After conversation with Gov't climate expert, he advises that the 9.8 Gt is only "human related", which corresponds to the 332 Tg or Mt x 28 GWP for IPCC CO₂-e = 9.3 Gt. Much closer!
Thx to the website. Cheers. Roger

[pigkang]

In atmospheric chemistry, it’s important to accurately convert methane (CH₄) emissions to their carbon dioxide (CO₂) equivalent to assess their climate impact. To clarify the unit conversions:

1 teragram (Tg) equals 10¹² grams.

1 megaton (Mt) is 1 million tons, which equals 10⁹ kilograms, or 10¹² grams.
This means that 1 Tg = 1 Mt — both represent 10¹² grams.

When converting methane to its CO₂ equivalent, the ratio is based on their molecular weights:

The molar mass of CO₂ is 44 g/mol

The molar mass of CH₄ is 16 g/mol So, the ratio CO₂/CH₄ is 44/16 = 2.75.

This means that 1 Mt of CH₄ is equivalent to 2.75 Mt of CO₂ in mass terms.

Given this, the statement that 9.8 Gt = 622 Tg is incorrect because:

9.8 Gt (gigatons) is 9,800 Mt

622 Tg is 622 Mt Clearly, 9,800 Mt ≠ 622 Mt.

[ChenBeier]

Already discussed above.
No need to extend the threat with no new information.